Muscle metaboreflex activation increases ventilation and heart rate during dynamic exercise in humans

Area of Science:

• Exercise Physiology
• Cardiorespiratory Control
• Skeletal Muscle Afferents

Background:

• Thin-fibre skeletal muscle afferent neurotransmission influences exercise responses.
• Stimulating muscle metaboreceptive afferents at rest via postexercise circulatory occlusion (PECO) typically does not elicit ventilatory or heart rate changes.
• The role of muscle afferent feedback in ventilatory control may only be evident during exercise when central respiratory drive is elevated.

Purpose of the Study:

• To investigate if muscle metaboreceptive afferents contribute to ventilatory control during exercise.
• To examine if the effects of PECO on cardiorespiratory responses are revealed during concurrent exercise.

Main Methods:

• Healthy participants performed single-legged cycling exercise at 40 or 60 W.
• Postexercise circulatory occlusion (PECO) was applied to the exercising leg during contralateral leg exercise.
• Cardiorespiratory responses (ventilation, heart rate, gas exchange) were measured with and without PECO.

Main Results:

• Ventilation was significantly higher during 60 W contralateral exercise with PECO compared to control.
• Heart rate responses were significantly greater during contralateral exercise with PECO at both 40 W and 60 W.
• No significant differences in oxygen uptake, carbon dioxide production, or perceived exertion were observed between conditions.

Conclusions:

• Stimulation of muscle metaboreceptive afferents can increase ventilation and heart rate during dynamic exercise.
• These findings suggest that metaboreceptive muscle afferents play a role in the control of exercise hyperpnea.
• The involvement of these afferents in cardiorespiratory control is more apparent during exercise than at rest.